Tesla App Energy Production: DC or AC?

[vanR]

Regarding Tesla solar energy products: Is the production of power (kW) and energy (kWh) *as shown in the Tesla app* either DC (before inverter losses) or AC (after inverter losses)?

For PV array performance monitoring, I would want DC. For utility bill comparison purposes, I would want AC. My guess is that it is DC, but I could not find any documentation on this. If you know the answer, can you also provide the source?

 

[jjrandorin]

I dont have any documentation, and I am only guessing, however a powerwall is an AC coupled device, so I doubt very seriously its DC.

 

[jgleigh]

The Tesla app is going to show AC since it's showing the output from the inverters, but you can access the direct DC numbers (and a ton more information) in the API.

At least in my setup, the output of the solar inverters is also monitored with CT clamps so there's additional errors introduced.

 

[vanR]

The Tesla app is going to show AC since it's showing the output from the inverters, but you can access the direct DC numbers (and a ton more information) in the API.

At least in my setup, the output of the solar inverters is also monitored with CT clamps so there's additional errors introduced.

Can you provide a reference showing that the app displays AC?

 

[jgleigh]

None of this is officially documented.

 

[zƬesla]

you can access the direct DC numbers (and a ton more information) in the API.

Perhaps assuming it's a Tesla inverter. For other inverters, you'd probably have to use their API (not Tesla's) to get the info.

 

[aesculus]

Regarding Tesla solar energy products: Is the production of power (kW) and energy (kWh) *as shown in the Tesla app* either DC (before inverter losses) or AC (after inverter losses)?

For PV array performance monitoring, I would want DC. For utility bill comparison purposes, I would want AC. My guess is that it is DC, but I could not find any documentation on this. If you know the answer, can you also provide the source?

As @jjrandorin states it's all AC. There are CTs placed everywhere on the circuits going to and from the PWs and Gateway, house loads, solar etc. They measure AC current and along with the voltage show the power (kW). What an inverter does individually is different. It may have the ability to show AC and DC, but this is not displayed on the Tesla app. It only shows the AC kW so it's all in the same format and units.

 

[vanR]

Why did I guess DC instead of AC:

Over a 31-day period, the Tesla app reported a 7% lower yield compared to the utility meter*, which could correspond to an average inverter efficiency of 93%, which seemed plausible. The yield was based on the 5 minute-increment source data downloaded from the app (without using the API in an automated manner). However, using the app's day-increment yield data, the difference significantly changes to a 13% lower yield.

Also, for my second (separately metered) solar roof, the 5 minute-increment based yield was "only" 1% lower, so that would then correspond to a fictitious 99% average inverter efficiency, which is not realistic as far as I know. Use of the day-increment yield data results is a 4% lower yield, so again a significant change there.

Based on these inconsistencies and the comments above, at this point I am assuming:

1. the app shows AC power and energy,
2. the utility energy meters' accuracy is significantly better than that of Tesla,
3. the Tesla app has some bugs, leading in inconsistent yields (summation of 5-min incr data VS daily yield numbers).

*SMUD (Sacramento) - measures AC generation at solar inverter.

 

[jgleigh]

Tesla app definitely has issues. I get much better data pulling it from the API and graphing it myself.